Selection requirements for vacuum pump oil

1. Sealing of vacuum pump oil

With suitable viscosity vacuum pump oil demand, the rapid start at low temperature can make the vacuum pump, vacuum pump oil at high temperature can have good sealing, within the pump vacuum pump oil has low temperature rise. It does not contain light volatile components and reduces the oil return rate of vacuum pump during operation.

2. Saturated vapor pressure of vacuum pump oil

Saturation vapor pressure is one of the key indexes of vacuum pump oil. In a closed container with constant temperature, the pressure is called saturation vapor pressure when the vapor-liquid two phases reach dynamic equilibrium.
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The saturated vapor pressure of the oil should be as low as possible. At the highest operating temperature of the pump, the saturated vapor pressure should be low enough and lower than the limit pressure of vacuum pump rules. Under the condition of 60 ℃ temperature to reach at least six. 5 x 10-5 kPa (for every temperature 20 ℃, saturated vapor pressure falling about an order of magnitude).
3. Ultimate total pressure and ultimate partial pressure of vacuum pump oil
Ultimate total pressure: the total pressure produced by all substances (gases) of the vacuum pump is measured by pyranimeter or thermocouple vacuum meter. At present, foreign countries pay attention to the test indicators of total pressure.

Limit partial pressure: the limit partial air pressure of the pump measured by the mercury tight vacuum gauge (MCT), the partial pressure of the double-stage rotary vane pump should be no more than 6 * 10-5kpa. Limit total pressure and limit pressure difference request is not more than an order of magnitude. The greater the difference between the two, the more volatile components the vacuum pump oil contains and the worse the properties of the oil.

water ring vacuum pump Note for selecting

I. determination of water ring vacuum pump type

The type of water ring vacuum pump is mainly determined by the medium pumped, the amount of gas required for work, the degree of vacuum or the exhaust pressure.
After the water ring vacuum pump works normally, two points should be noted:
Vacuum pump is used in petrochemical industry

1, as far as possible demands the selected vacuum degree of vacuum pump in efficient interval, which is the critical need critical area of the exhaust pressure or vacuum operation, so as to ensure the vacuum pump according to the conditions and requirements to work properly. Avoid operating near the maximum vacuum degree or maximum exhaust pressure range of the vacuum pump. Operating in this area, not only is the efficiency extremely low, but also the work is very unstable, easy to make the vacuum pump vibration and noise. For vacuum pumps with high vacuum degree, cavitation often occurs during operation in this area. The obvious phenomenon is noise and vibration in the vacuum pump. Excessive cavitation will lead to damage of pump body, impeller and other parts, so that the vacuum pump can not work properly.

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It can be seen that when the vacuum degree or gas pressure required by the vacuum pump is not high, it can be selected from the single-stage pump first. If higher requirements for vacuum or exhaust pressure, single pump often can not meet, or demand under the condition of high vacuum pump still has large volume, which requires performance curve at higher vacuum degree is relatively flat, can choose two stage pump. If the vacuum degree is above -710mmhg, the roots water ring vacuum unit can be selected as the vacuum extraction device.

2. Select the vacuum pump correctly according to the amount of gas required by the system

If selected or vacuum unit type vacuum pump, also need to according to the swept volume required by the system to choose the right model (on the extraction rate of vacuum equipment selection and extraction time can refer to a single product of our company introduction).Main parameters of vacuum pump

vacuum pump matters needing attention

1. The working pressure of the vacuum pump should meet the requirements of the extreme vacuum and working pressure of the vacuum equipment. For example, the working vacuum of 10mmHg is required by a certain vacuum drying process, and the ultimate vacuum of the selected vacuum pump should be at least 2mmHg, preferably up to 1mmHg. The limit vacuum of the pump is usually half to an order of magnitude higher than the operating vacuum of the vacuum equipment.

2. Select the working point of the vacuum pump correctly. Each pump has a certain working pressure range, such as: 2 bv series water ring vacuum pump working pressure range 760 MMHG ~ 25 MMHG (pabs), in such a wide pressure range, the pumping speed of the pump vary with the pressure change (details refer to the changes of the pump performance curve), its stable working pressure range is 760 ~ 60 MMHG. Therefore, the working point of the pump should be selected within this range, rather than allow it to work for a long time under 25-30mmhg.

3. Under the working pressure, the vacuum pump should be able to drain all the gas produced in the process of the vacuum equipment.

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4. Combine the vacuum pump correctly. Because the vacuum pump has the selective pumping, so, sometimes choose a kind of pump can not meet the pumping requirements, several kinds of pumps need to be combined to supplement each other to meet the pumping requirements. Such as titanium sublimation pump for hydrogen has a high pumping speed, but it can't take helium, sputtering ion pump and three pole type, type (or two extremely asymmetric cathode sputtering ion pump) to the argon pumping speed to a certain extent, the two together, will make the vacuum unit get good vacuum degree. In addition, some vacuum pumps can't work under atmospheric pressure and require prevacuum. Some vacuum pump outlet pressure is lower than atmospheric pressure, the need for the front stage pump, so the combination of the pump.

5. Requirements of vacuum equipment for oil pollution. If the equipment strictly requires no oil, should choose a variety of non-oil pumps, such as: water ring pump, molecular sieve adsorption pump, sputtering ion pump, low temperature pump, etc. If the requirements are not strict, the oil pump can be selected, and some anti-oil pollution measures, such as cold trap, baffle plate, oil trap, can also meet the requirements of clean vacuum.

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6. Understand the components of the gas being pumped, including non-condensable vapor, particle dust, corrosion, etc. When selecting a vacuum pump, it is necessary to know the gas composition and select the corresponding pump for the gas being pumped. If the gas contains vapors, particles, and corrosive gases, consideration should be given to installing auxiliary equipment, such as condensers, dust collectors, on the inlet pipe of the pump.

7. How does the oil vapor from the vacuum pump affect the environment? If the environment is not allowed to be polluted, you can choose a non-oil vacuum pump, or oil vapor out of the room.

8. Whether the vibration produced during the operation of the vacuum pump has any influence on the process and environment? If the process is not allowed, the non-vibrating pump should be chosen or anti-vibration measures should be taken.

9. Price, operation and maintenance cost of vacuum pump.

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